Two stages of accelerated exhumation in the middle reach of the Yarlung River, southern Tibet since the mid‐Miocene

In the mid-1950's, fingernail clams virtually disappeared from a 100-mile section of the IL River, a tributary of the Mississippi River, due to unknown causes. A survey of the bottom fauna of the IL River in 1979, revealed that the clams were still absent from the middle reach of the River, where they had been abundant prior to the die-off in the 1950's. Some factor(s) in the River currently prevent the clams from recolonizing areas where they were formerly abundant. Recently, clams exposed to fluoride developed abnormal grooves in the shell matrix. Fluorides are known to be protoplasmic poisons removing essential body calcium by precipitation. Since the shell consists primarily of Ca carbonate, this investigation examines the possible role of fluoride on shell formation and the poisoning of the Ca pump which can directly inhibit lateral ciliary activity on the gill.

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Altered Fine Structure of B Lymphocytes Correlated with Defective Terminal Differentiation

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010007237x ◽

1973 ◽

Vol 31 ◽

pp. 386-387

Author(s):

Dale E. Bockman ◽

L. Y. Frank Wu ◽

Alexander R. Lawton ◽

Max D. Cooper

Keyword(s):

Immune Deficiency ◽

B Lymphocytes ◽

Plasma Cells ◽

Present Report ◽

Specific Antigen ◽

Terminal Differentiation ◽

Second Stage ◽

Two Stages ◽

Deficiency Diseases ◽

Cell Line Generation

B-lymphocytes normally synthesize small amounts of immunoglobulin, some of which is incorporated into the cell membrane where it serves as receptor of antigen. These cells, on contact with specific antigen, proliferate and differentiate to plasma cells which synthesize and secrete large quantities of immunoglobulin. The two stages of differentiation of this cell line (generation of B-lymphocytes and antigen-driven maturation to plasma cells) are clearly separable during ontogeny and in some immune deficiency diseases. The present report describes morphologic aberrations of B-lymphocytes in two diseases in which second stage differentiation is defective.

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Formation of Dislocation Channels in Neutron Irradiated Molybdenum

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100096618 ◽

1972 ◽

Vol 30 ◽

pp. 672-673

Author(s):

S. Mahajan

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Ambient Temperature ◽

Room Temperature ◽

Channel Formation ◽

Early Stages ◽

Transmission Electron ◽

Three Stages ◽

Two Stages ◽

Polycrystalline Molybdenum

The evolution of dislocation channels in irradiated metals during deformation can be envisaged to occur in three stages: (i) formation of embryonic cluster free regions, (ii) growth of these regions into microscopically observable channels and (iii) termination of their growth due to the accumulation of dislocation damage. The first two stages are particularly intriguing, and we have attempted to follow the early stages of channel formation in polycrystalline molybdenum, irradiated to 5×1019 n. cm−2 (E > 1 Mev) at the reactor ambient temperature (∼ 60°C), using transmission electron microscopy. The irradiated samples were strained, at room temperature, up to the macroscopic yield point.Figure 1 illustrates the early stages of channel formation. The observations suggest that the cluster free regions, such as A, B and C, form in isolated packets, which could subsequently link-up to evolve a channel.

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